Tim Thomas wrote:
I don't know enough about how ZFS manages memory other than what I have
seen on this alias (I just joined a couple of weeks ago) which seems to
indicate it is a memory hog...as is VxFS so we are in good company. I
am not against keeping data in memory so long as it has also been
written to somewhere non-volatile as well so that data is not lost if
the lights go out... and applications don't fight for memory to run. I
recall stories from years ago where VxFS hogged so much memory on a Sun
Cluster node that the Cluster services stalled and the cluster failed over!
Even after many years, I can still get mileage from this one :-)
http://www.sun.com/blueprints/0400/ram-vxfs.pdf
ZFS behaves differently, however, so the symptoms and prescriptions are
slightly different.
I need to go read some white papers on this...but I assume that
something like direct I/O (which UFS, VxFS and QFS all have) is in the
plans for ZFS so we don't end up double buffering data for apps like
databases ? - that is just ugly.
Before you get very far down this path, it gets regularly rehashed here,
so Roch Bourbonnaise and Bob Sneed wrote some good blogs on the topic.
Especially:
http://blogs.sun.com/bobs/entry/one_i_o_two_i
http://blogs.sun.com/roch/entry/zfs_and_directio
-- richard
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